The present invention relates to a pumping unit for enteral, parenteral or infusion feeding, comprising a single-use pumping chamber provided with an inlet duct, a delivery duct and an elastically deformable pumping membrane, a pusher for alternately deforming the deformable membrane, said driving pusher being housed in a support casing one wall of which has a retaining slideway with which the sliding elements of the pumping chamber engage, this support casing also having a through-opening for the driving pusher, and abutment means for determining the position of the pumping chamber along the retaining slideway and for putting said pumping membrane into drive connection with said driving pusher.
The majority of pumping units used in this type of application employ peristaltic pumps. The drawback with this type of pump is its very poor efficiency owing to friction inherent in its design. As a result, it is not possible to pump more than about 3 liters with a battery supplying around 26 000 J. This limited pumping capacity between battery recharges constitutes a major drawback which makes ambulatory use problematical.
Another drawback with these pumps results from the installation of the tubing between the tube-deforming pads or rollers and the cylindrical bearing surface of this tube with respect to which the pads or rollers are driven. The pump can only operate if the flexible tube is correctly positioned. In order to avoid the risk of incorrect installation, it is generally proposed for that part of the flexible pipe that engages with the pump rollers, and also the bearing surface against which the tube is deformed, to be provided in a cassette which has means for fastening it to the roller drive mechanism.
U.S. Pat. No. 5,647,852 proposes a piston pump in the form of a cassette comprising means for its positioning and removable fastening on a drive mechanism having a linear motor. Such a pump is used for lavage in the medical, dental and therapeutic fields.
WO 2005/030299 proposes a pumping device with a cassette provided with control and pumping membranes, where the cassette is introduced into a slideway of a carriage which is itself mounted such that it slides on a framework comprising the pumping cassette drive mechanism. Once the cassette has been installed on the carriage, the latter is pushed back toward the framework in order to put the operating membranes in contact with driving pushers.
The main drawback with this device is its complexity and thus its cost and reliability. In addition, preloading of the pumping membrane results from the carriage moving along the same course as that along which the control pusher of this membrane is moved, but in the opposite direction. Thus, if the carriage, when it has been pushed back toward the framework, is not in exactly the right position, the stroke of the membrane and thus the volume pumped will vary.